This invention relates to a method and apparatus for thermal insulation, and more particularly, to a thermal break means for use in windows and doors of building structures.
In the construction of building structures, it has been long recognized that a thermally "tight" structure aids in the prevention of drafts, the reduction of fuel bills and other desirable benefits. It is also known that in an otherwise well insulated building, major heat losses may be attributed to the openings in the building, specifically the doors and windows. In conventional applications, air has been used as the chief insulative means between the exterior surface and the interior surface. Of course, the most widely used is the conventional storm window which is generally attached to the building itself and is spaced one to three inches from the interior window. Another popular form of insulation for windows is the double pane method of glazing, wherein two panes of glass are hung parallel to one another and spaced roughly one-eigth of an inch by a rigid, non-conductive material such as wood and sealed air tight by a suitably resilient non-conductive material.
In the manufacture of windows with metal frames and doors with metal exteriors, various undesirable aspects of metal have been accepted in view of the overriding advantages of such a metal frame. For example, metal frames result in reduced maintenance since there is no painting or other upkeep as with wooden frames. Further, the metal does not warp or rot. However, such a frame is inherently an excellent conductor of heat, thereby causing a loss of building heat in the winter and a gain of building heat in the summer. In the winter the temperature differential between the frame and the inside air causes sweating on the frame surfaces as the interior moisture-laden air condenses on the cold surfaces of the frame. This condensation, if severe enough, will drip down and cause damage to walls, woodwork and sashes.
Various measures have been taken to prevent or retard this thermal conductivity of the exterior frame surfaces with the interior frame surface. These measures include windows having separate interior and exterior metal surfaces separated from each other through strips of rigid vinyl plastic or other semi-resilient insulative means. Other measures have included extruded parts which, when placed together, form a pocket which is filled with an initially flowable insulative medium such as a resin or the like. This insulative medium is cured within the pocket, and the ends of the extruded pocket-forming pieces cut away, leaving a metal frame having an interior and an exterior portion, each joined to the other through an insulative medium, thereby creating an effective thermal break between the exterior and interior surfaces of the frame. However, the expense of manufacturing such a frame is high due to the final step of cutting the frame to form the thermal break, a time consuming procedure.